Water contains organic matter, dissolved solids and minerals that deposit scale and film on surfaces in drinking water distribution pipes and equipment. Quality and flow of drinking water is deleteriously affected by these scales and films. In addition, many cleaning and sanitizing agents leave film residues. Use of the methods and compositions described herein control these deposits.
A variable matrix of organic and inorganic deposits accumulates on the interior surfaces of all drinking water distribution piping systems. Control of such deposits is the key to improved water quality, lower maintenance costs and efficient use of disinfectants. Organic-laden deposits of this kind are a significant source of increased chlorine demand and they can produce precursors of trihalomethanes and haloacetic acids disinfection byproducts. Variously called biofilms, scale or tuberculations, many deposits in drinking water systems have been shown to harbor and protect pathogenic or otherwise troublesome bacteria, viruses, algae and algal toxins, fungi, protozoa and invertebrates. Many types of microorganisms can proliferate in such deposits, and their toxic by-products can become problematic. Regardless of the level of residual disinfectant, microorganisms within these harborage deposits have been proven to periodically slough off and re-entrain into the flowing water, thereby contaminating other systems and exposing susceptible consumers to biological hazards from drinking water systems in the buildings they occupy.
Nearly everyone is familiar with “scale” such as occurs in a tea pot used with hard water. The white precipitate is calcium carbonate and it deposits onto the surface of the pot because the solubility of the salt is inversely related to temperature: as the temperature increases, the salt precipitates. But in drinking water systems, the scaling process is more complex and the water is not boiled (boiling water has a very destructive effect on organic compounds in water). Deposits in drinking water systems never include just calcium carbonate (or other inorganic substances). This is because organic materials in the water are prone to adhering to surfaces. Native organic compounds from bulk drinking water accumulate onto surfaces because adsorption is thermodynamically favored. Consequently, the deposits on surfaces in drinking water distribution systems include organic compounds and inorganic compounds such as “scale”. These organic materials give the deposit characteristics which are much different than those scale deposits seen on the surface of a tea pot, for example.